Fix grammar

docs/context.dox

@@ -115,7 +115,7 @@ Buffer swapping is part of the window and framebuffer, not the context.  See
 
 @section context_glext OpenGL and OpenGL ES extensions
 
-One of the benefits of OpenGL and OpenGL ES are their extensibility.
+One of the benefits of OpenGL and OpenGL ES is their extensibility.
 Hardware vendors may include extensions in their implementations that extend the
 API before that functionality is included in a new version of the OpenGL or
 OpenGL ES specification, and some extensions are never included and remain

docs/quick.dox

@@ -230,7 +230,7 @@ glViewport(0, 0, width, height);
 @endcode
 
 You can also set a framebuffer size callback using @ref
-glfwSetFramebufferSizeCallback and call `glViewport` from there.
+glfwSetFramebufferSizeCallback and be notified when the size changes.
 
 Actual rendering with OpenGL is outside the scope of this tutorial, but there
 are [many](https://open.gl/) [excellent](http://learnopengl.com/)